1. Field of the Invention
The present invention relates generally to improvements in the production of cold mix asphalt and, more particularly, but not by way of limitation, to the production of cold mix asphalt from material planed from a roadway in an apparatus towed by the roadway planer during roadway planing operations.
2. Brief Description of the Prior Art
It has long been recognized that considerable savings can be achieved in the refurbishing of a roadway by using the roadway itself as a source of paving material. Thus, a number of machines have been constructed to disintegrate an upper layer of a roadway within a hood while asphaltic composition, that is, a heavy oil, is injected into the hood so that cold mix asphalt is mixed within the hood while the disintegration of the layer of the roadway occurs. The cold mix asphalt can then be compacted to form a new driving surface for the roadway.
While the repaving of a roadway in this manner is useful in a number of circumstances, other circumstances exist in which the resulting refurbished roadway will not be adequate to the demands that will be placed on the roadway. In particular, because of the lack of control of the aggregate-to-asphaltic composition ratio of the resulting cold mix asphalt, the quality of the cold mix asphalt may not meet required standards. In these circumstances, it is necessary either to produce the asphalt elsewhere and deliver it to the roadway or to provide expensive mechanisms on a traveling cold mix plant to precisely fix the ratio of aggregate to asphaltic composition that is produced in the plant. For example, it is known to weigh material that is cut from a roadway as the material is introduced into a pugmill and then meter asphaltic composition into the pugmill in accordance with the weight of material that has been introduced into the pugmill. While this approach is workable, it suffers from several disadvantages. Initially, the weighing of the material cut from a roadway; that is, the aggregate from which the new cold mix asphalt is formed, requires expensive equipment and such equipment can be sensitive to vibration as the cold mix asphalt plant is drawn along the roadway so that the ratio of aggregate to asphaltic composition can undergo a considerable variation as the cold mix asphalt is produced.